According to present-day prior art, SGRAM (synchronous graphics random access memory) products comprise chips with a peripheral arrangement of bonding pads, i.e., bonding pads are arranged along the outer edges of the chip. Also, the products have a housing in traditional face-up technology. This means that the chips are bonded onto a substrate with the active side upward. For electrical contact connection, wire bridges connect the bonding pads on the chip to the contact islands on the substrate on the chip side. The substrate is furthermore provided with soldering balls on the side opposite to the chip, which are connected to the contact islands via a rewiring in the substrate. In order to be able to realize this, multilayer substrates are used. Such packages are also referred to inter alia as an FBGA arrangement (Fine Pitch Ball Grid Array).
Calculations by chip designers have now shown that it is no longer possible to realize the peripheral arrangement of the bonding pads for DDR3 SGRAMS and comparable components owing to the high clock rate of 800 MHz and owing to the signal propagation times. Furthermore, significantly lower signal and supply inductances than according to the present-day standard are required.
In order to prevent these problems, an arrangement of the bonding pads along the chip center axis (center pad row) is required. However, such an arrangement of the bonding pads is difficult to realize in the case of SGRAM products owing to the high number of pads. For example, the number of pads rises to more than 130 in products of this type. This results in the requirement for a new housing technology.
Such a housing technology would have to support the center pad row and at the same time have low electrical parasitics (short signal propagation times, low signal and supply inductance). What is more, a high number of bonding pads must be possible.
The BOC-BSP (board on chip—backside protection, that is to say a chip size package with backside protection) platform technology realized at the present time cannot satisfy these requirements. With the one-layer substrate used hitherto the parasitics cannot be adapted to the required extent.